A wind turbine known in the art comprises a wind turbine tower and a wind turbine nacelle positioned on top of the tower. A wind turbine rotor with a number of wind turbine blades is connected to the nacelle through a low speed shaft, as illustrated on FIG. 1.
Large modern wind turbines typically comprise more than one temperature control system for controlling the temperature of different wind turbine components such as gearbox, generator or inverter.
A temperature control system will in most cases be the equivalent of a cooling system, in that the wind turbine components typically are producing heat during normal operation of the wind turbine, which needs to be removed to ensure the life and the efficiency of the component. But under some circumstances the temperature control system could also be used to heat up the component e.g. during start-up, in very cold environments or other.
Most temperature control systems comprise a fluid in the form of a refrigerant or coolant with advantageous qualities regarding transporting heat but sometimes this fluid has to fulfil other purposes than just transporting heat. E.g. in the gearbox of the wind turbine large amounts of oil are circulating to ensure lubrication of different parts of the gearbox. An operating gearbox produce heat and this heat are typically removed from the gearbox by means of the circulating oil which e.g. transports the heat to a radiator that gives off the heat to the surroundings.
But the lower the surrounding temperature is, the colder the oil becomes during its flow through the radiator, and the colder oil is, the higher its viscosity becomes hereby increasing the risk of the oil clogging the radiator or other part of the system.
An object of the invention is to provide for an advantageous technique for ensuring that the temperature of fluid circulating in a temperature control system in a wind turbine is controlled more advantageously.